In recent years, a photovoltaic cell that receives sunlight to generate power is becoming widely used among power consumers. Along with the wide use of the photovoltaic cell, a grid interconnection apparatus (so-called power conditioner) that interconnects the photovoltaic cell to a commercial power grid (hereinafter, “grid”) to supply power to a load is also becoming widely used.
The grid interconnection apparatus has a grid interconnection relay for performing off-line of the photovoltaic cell from the grid (see Patent Literature 1, for example).
The grid interconnection apparatus is configured to perform interconnection stop control that detects a state where an output power amount of the grid interconnection apparatus is too small with respect to a power consumption amount of the load (at nighttime, for example), turns off a grid interconnection relay to perform off-line of the photovoltaic cell from the grid, and stops operation of the grid interconnection apparatus.
Further, the grid interconnection apparatus performs startup control that detects a state where output power of the photovoltaic cell can be acquired, turns on the grid interconnection relay to interconnect the photovoltaic cell to the grid, and starts an interconnected operation.